When GOP Sen. Orrin G. Hatch announced Tuesday that he will retire from the Senate after serving Utah for more than four decades, talk quickly turned to whether Mitt Romney will seek to succeed him.

But on Capitol Hill, the pending departure of the Finance Committee chairman — who could have wielded the tax writing gavel for two more years under conference rules — also raises questions about which senator will lead the GOP on taxes, trade, health care and entitlements.

The chamber has always given deference to seniority, meaning that if the GOP keeps control of the Senate, the focus will be on Judiciary Chairman Charles E. Grassley.

The Republican from Iowa took to his always active Twitter account Tuesday to wish Hatch well.

“Sen Hatch is a friend for 37 yrs while serving together in US Senate. He serves Utah & USA w tremendous success as effective as can be & deserves credit 4 doing so,” Grassley wrote.

Arriving in the Senate just four years after Hatch, Grassley has served alongside him for decades on both the Finance and Judiciary panels.

Hatch: Time to ‘Hang Up the Gloves’

Grassley previously served as chairman of the Finance panel from 2003 until the Democrats gained the majority in 2007, working closely with Democratic Sen. Max Baucus of Montana. He was also the chairman in 2001 during the brief period of a deadlocked 50-50 Senate, until Sen. Jim Jeffords of Vermont switched caucuses and swung the majority to the Democrats.

The view of the Senate Republican Conference has been that terms of service in a leadership role lasting less than a full two years should not be counted against internal term limits, which allow for only three two-year terms as chairman.

Weighing the options

A move back to leading the Finance panel in the final two years of President Donald Trump’s first term could be appealing to Grassley. But with scores of appellate court seats to fill, along with the potential for additional Supreme Court nominations, he might well choose to continue on the Judiciary Committee.

Should Grassley go to Finance, it would be Sen. Lindsey Graham on deck at Judiciary. A former campaign adversary of Trump, the South Carolina Republican has emerged as a vocal supporter of the president. He also brings a legal background as a former military lawyer, serving as an instructor for the Air Force Judge Advocate General’s School and as a judge.

Graham has become a frequent golfing partner for Trump at the president’s course in Northern Virginia and elsewhere.

If Grassley were to opt to remain atop the Judiciary Committee, the next man in line at Finance would be Michael D. Crapo of Idaho. The current Banking chairman would likely be replaced in that role by Pennsylvania Sen. Patrick J. Toomey.

As for Romney, he thanked Hatch for his years of service in a Facebook post. Romney did not indicate whether he would run for Hatch’s seat, though he is widely considered to be a potential candidate.

Freezing the field

Hatch’s decision came on the first day that candidates could declare their intention to gather signatures, one of two paths to the ballot in Utah.

Waiting until the final hour essentially froze the rest of the GOP field, said LaVarr Webb, a GOP consultant and publisher of UtahPolicy.com.

“It’s really late in the year, late in the cycle, for anyone who is not independently wealthy or famous, someone with great name ID, to get into the race and be a credible candidate,” Webb said.

Romney fits the bill across that particular board. Webb said Romney could face some pushback from Trump supporters or far-right conservatives who view Romney as too moderate, but it’s unclear who would be willing to challenge the former Massachusetts governor and 2012 GOP presidential nominee.

In that race, Romney became the first Mormon to lead a major party’s presidential ticket. Mormons make up about 55 percent of Utah’s population, and Romney carried the state in 2012 with 73 percent of the vote.

More recently, mainstream Republicans in Utah have appreciated Romney’s willingness to speak out against Trump, Webb said.

In making his retirement announcement, Hatch highlighted some of his own legislative accomplishments.

“I’ve authored more bills that have become law than any member of Congress alive today. I played a central role in the creation of the modern generic drug industry, the passage of the landmark Americans with Disabilities Act and the confirmation of every current member of the United States Supreme Court. Just last month, I helped lead the effort to pass historic, comprehensive tax reform,” Hatch said in a video.

Hatch was one of the lead authors of the Children’s Health Insurance Program, along with Democratic Sen. Edward M. Kennedy of Massachusetts, and its stalled reauthorization is poised to be a key priority for Hatch in his final year as a senator.

Other plans for 2018 include teaming up with Tennessee Republican Lamar Alexander to update payments to songwriters in the age of digital and streaming music. Hatch is himself a songwriter and musician.

The 83-year-old Hatch had been encouraged to run again by Trump, with whom he had a close relationship.

He once tried running for president himself, mounting a quixotic campaign in 2000 and finishing last in the caucus field in Iowa.

Beyond his record on legislation and nominations, Hatch serves as the president pro tempore of the Senate, which is a constitutional office in the line of presidential succession.

By custom, the office is held by the most senior member of the majority party. Next in line is Senate Appropriations Chairman Thad Cochran.

The Mississippi Republican has been plagued by health challenges lately, and his aides have denied any plans for an announcement of an early retirement. But some senators think that Cochran may step aside sooner rather than later.

In line to be the president pro tempore after Hatch and Cochran? Once again, it’s Grassley.